Electrostatic charge is the result of electrification of an object such that the charge is confined to the object. Friction between two surfaces in close contact typically gives rise to electrostatic charge or static electricity.
Textiles and plastics generally have low conductivity and dissipate charge at a relatively low rate. While it has been proposed to attenuate electrostatic charge build-up on textile and plastic materials by reducing its rate of generation, friction is inherent in many plastics and textile processing operations, particularly the latter, and cannot be substantially reduced. Consequently, increasing the rate of electrostatic charge dissipation of a textile or plastic material by increasing its electrolytic conductivity through the application of internal or external antistatic agents is commonly used as a means of controlling electrostatic build-up in such materials.
External or surface antistatic agents are directly applied as a coating to the surface layer of a textile or formed plastic substrate, typically dissolved or suspended in a suitable vehicle, such as water or another solvent. Internal antistatic agents are commonly used in formed plastic substrates and are physically mixed or blended with the resin mass prior to the forming operation, e.g., spinning, drawing, molding or the like, so as to be uniformly distributed throughout the body of the finished product, including the surface layer. Internal antistatic agents generally provide a longer lasting electrostatic charge dissipative effect.
One particularly notable benefit of antistatic agents is the reduction of undesired attractive forces between static prone objects treated therewith, such as so-called "static cling". In addition, treatment with antistatic agents diminishes the hazard potential of plastic packaging and other plastic products which otherwise might result in explosion when present in areas where flammable gases are used, or in damage to charge-sensitive products exposed thereto, e.g. semiconductors.
Antistatic agents have other advantages. For example, treatment of polyester and nylon fabrics with antistatic agents has been shown to reduce fabric soiling. Static-prone plastic articles, such as packaging materials, that are treated with antistatic agents resist accumulation of dust and thus are more attractive for packaging of consumer products. Antistatic agents are also used for enhancing the receptivity of plastic surfaces to electrostatically applied coatings, e.g., in automobile production.
Various chemicals have been proposed for use as antistatic agents, including, by way of example, long-chain amines, amides and quaternary ammonium salts; esters of fatty acids and their derivatives; sulfonic acids and alkyl aryl sulfonates; polyoxyethylene derivatives; polyglycols and their derivatives; polyhydric alcohols and their derivatives; and phosphoric acid derivatives.
Particularly good antistatic effects have been obtained using antistatic compositions comprising the reaction product of a polyaminoamide having unreacted primary and secondary amine groups and a halohydrin derivative. These antistatic agents have been found to be stable and not transient when used in textile and plastics processing. That is to say, an amount of antistatic agent sufficient to provide effective electrostatic charge dissipation is retained on the surface of the coated substrate, whether textile or plastic, until processing is complete. It has been discovered, however, that the last-mentioned antistatic compositions in certain applications, develop undesirable levels of surface tackiness upon drying. In particular, in applying antistatic finishes to textile materials, tacky residue from the antistatic composition may be deposited on the textile processing equipment and interfere with normal operations.
In the processing of textiles and plastic materials, it is also very desirable to impart thereto lubricating properties, for example, to improve handling properties and processing speeds. Thus, finishing compositions are generally applied to textile fibers to improve their subsequent handling and processing. Fiber finishes play an important role in assisting the fiber producer to manufacture the product, and enable the fiber producer's customers to carry out the required yarn and fabric manufacturing processes to obtain the finished textile product. The composition and amount of finish composition applied depend in large measure upon the nature, i.e., the chemical composition of the fiber, the particular stage in the processing of the fiber, and the end use under consideration.
For example, compositions referred to as "spin finishes" are usually applied to textile fibers after extrusion. These or other finishes which may be applied to yarn prior to knitting or winding, and to fiber tows prior to or at the time of crimping, drying, cutting, drawing, roving, and spinning, or to staple fibers prior to carding, i.e., web formation, and subsequent textile operations such as yarn manufacture or preparation of nonwoven webs are commonly called secondary or over-finishes. Such finishes provide lubrication, prevent static build-up, and afford a slight cohesion between adjacent fibers.
The application of such finishes is generally accomplished by contacting a fiber tow or yarn with a solution or an emulsion. Finish compositions can also be applied to tow, yarn, or cut staple by spraying.
Acceptable finishes must fulfill a number of requirements in addition to providing desired lubricating and antistatic effects. For example, they should be easy to apply (and to remove if desired), they should have good thermal and chemical stability, they should not adversely affect the physical or chemical properties of the fibers to which they are applied and they should aid the subsequent processes to which the treated fibers are subjected, they should not leave residues on surfaces or cause toxic fumes or undesirable odors, they should rapidly wet the fiber surface, they should be water-soluble or emulsifiable or solvent-soluble, they should have good storage stability, they should be compatible with sizes, nonwoven binders and other fiber treatments, they should not attract soil or cause color changes to the fibers, they should not interact with frictional elements used in texturizing and they should not be corrosive to machine parts.